System of electrical distribution.



No. 895,823. PATENTED, AUG. 11, 1908 J. L. WOODBRIDGE. SYSTEM OF ELEGTRIGAL'DISTRIBUTION.

APPLICATION FILED 0012, 1.907.

WITESSES nw/EmoR N JwepkZJIEadrdiga To all whom it may concern:

; n nnin JOSEPH LESTER WOO DBRIDGE, OF PHILADELPHIA, PENNSYLVANIA.

SYSTEM OF ELECTRICAL DISTRIBUTION.

Specification of Letters Patent Patented Aug. 11,1908.

Application filed October 2, 1907. Serial N 0. 395,516.

Be it known that I, JosEPn Lnsrnn W001) BRIDGE, a citizen of the UnitedStates, and resident of Philadelphia, in the county of Philadelphia and State of Pennsylvania,

have invented a certain new and useful System of Electrical Distribution, of which the following is as ecification. 7

My invention re ates to those sys'temsin which electrical energy is transformed from one frequency and number of phases to another and more particularly where polyhase electric currents are generated at one requency and utilized in the form of single phase electric currents at a lower frequency. One of the objects oimy invention is to provideless expensive and more efficient means than have heretofore. been used for transforming polyphase electric currents at one frequency into single phase electric currents at a lower frequency.

The eneral nature and scope of my invention wi lube more clearly understood by reference tothe following explanation in connection with the accompanying drawings, in which Figure 1, represents a phase and frequency chan er involving features of the invention, and Figs. 2, 3, and 4, are diagrammatic representations of the induction machine shown in Fig. 1, to which. reference will be made in explaining its 0 oration.

elr'errin to -ig. 1, G, is a single phase alternator ere shown of the revolving field biepolar type, the fields being excited by current from the exciter E, transmitted I through collectorrings on the-shaft the usual manner 'lhis alternator may, howi -ever,-.be designed in accordance with any of .40.

the standard methods well known in the art, and need not be more particularly described here; it being understood of course that the 1 number of poleso'f this alternator should correspond with the speed and frequency at Y which it is to be operated. is connected by the conductors 9 and 10, to the single. phase consumption circuit 1, 2,

This alternator supplying translating devices L. Y

Mounted on the shaft of the alternator is shown the rotor P, of an induction machine I. This rotor is provided with a winding 8, connected at four equidistant points a, b, c, d, to the four conductors 3, 4, 5, 6, respec tively of a two-phase supply circuit, The rotor P, is free to revolve in inductive rela- 7 tion to the stator S, which'latter is stationary and is provided with a windim 7-. Two 0 posite points of this stator Winding W and l, are connected by means of the conductors 12, and 11, in parallel with the alternator G, to the consumption circuit 1,- 2. Two other opposite pointsX and Z of the winding 7, displaced by an angle of-90 from the points ,W and V, are short circuited by means of the low resistance conductor 13. A switch K, is shown 'nterposed' in the conductor 11, which m y be used to disconnect this conductor from the conductor 2, of-the consumption circuit and'connect it by means of conductorl l, to the opposite point W", of the winding 7, thus short circuiting this winding across the points W and Y, for starting.

The operation of this apparatus is then as follows: With the switch K, in contact with conductor 14, the machine B, may be started from the polyphase supply circuit 3, 4, 5, 6, as an induction motor with short circuited armature in the usual manner. When, however, a speed of half that corresponding to synchronism with the supply circult is attained, the switch K, may be opened, and at the instant of proper phase relation between the electro motive force of. the induction machine I and the alternator G, the switch K, may be thrown into contact with conductor 2. The apparatus will then continue to operate at this speed correspondin to half the speed of synchronismand will develop an electro motive force across the conduotors 1,2, of the consumption circuit of half the frequency of the supply circuit The. load of the. translating devices L, will be divided equally between the two machines. Of the total'energy delivered by the supply circuit 3, l, 5, 6, to the rotor P, one-half wi l be transformed inductivelyand delivered as single phase current from the winding 7, to the consumption circuit 1, 2, while the other half will be transformed into mechanical c11 erg which will drive the alternntm' G to furnish the output which this alternator delivers to the consum tion circuit,

In order to exp ain more. vclearly the method of operation of the machine I, refcrencc will now he made to Figs. 2, 3, and 4, in which the rotor winding 8, and the stator winding 7, are represented by concentric circles. The direction of rotation of the rotor is indicated by the full line arrow 1'. Fig. :2, represents the relative position of rotor and stator at the instant when the chi-lro-uiolivc force of the supply circuit applied al the the points at, l), and 0, (Li

oints a, b, has reached its maximum value, while the electro-motive force applied at the points 0, d, is passing through zero. Durin the rotation of the rotor a small current wil flow between the points a, b, in phase with the applied electro-motive force, and similarly a small current will liow between the points 0, d, in phase with the electromotive force'applied to thesepoints, and therefore 90 behind that across the points a, b. In the absence of output to the circuit 1', 2, these currents will be limited to small amounts, by the counter electromotive force set up, as will be shown later, in the winding 8. These two currents will produce a small field represented by the light'arrow Ft, rotating in the direction of the dotted arrow f, opposite to the arrow 1". This small rotating field in phase with the electro-motive forces a )plied at points a, b, and c, (1, will produce e ectromotive forces in the winding 8, 90 behind this field and therefore-90 behind the applied clectro-motive forces. Thissame field will also produce a similar rotating elect-re motive force in the winding 7. The efi'ect of this small electro-n'iotive force in the winding 8, will be to cause currents to flow into said winding from the supply circuit at points a, b, and c, d, and these currents will be in phase with the small electro-motive force above mentioned and will therefore be 90 behind the applied electro-motive force at These currents will be of considerable magnitude, owing to the low resistance of the winding 8, and will constitute the true (wattless) magnetizing currents. At the instant illustrated inFig. 2, the wattless magnetizing current between the points a, b, and the field produced by it, are both passing through zero value, and since the electro-inotive force produced by such a field is in time quadrature, lagging, this .electro-motive force will be exactly counter to that applied across a, c, and just enough less than the latter to permit the small energy component of current iirst mentioned to flow. For if the counter electro-motive force were less than this a greater energy component of current would llow and this would cause a greater wattlcss component, which would increase the counter elcctro-motive force sufiiciently to establish equilibrium.

The wattless magnetizing current between the points (I, c, at the instant illustrated by Fig. 2, is at its maximum value and would )roduce afield in the direction (1, to 0, 90 bollind the field F, were it not l'or the current in the winding 7. noted above the small field F produces electro-motivc lorces in the winding 7, similar to those in 8, and since the points X and Z are connected by a comlnctor of low resistance, similar magnotiging currents will llow between the points Z as between the points c, d, and these .two will neuscenes I tralize each other and no field will be produced in this direction. l Fig. 4, represents conditions corresponding to an instant one half of a rimary cycle later l than Fig. 2. The small fie d F has made half l a revolution with respect to the winding 8, l but the winding 8, has been rotated onequarter revolution, bringing the point a, opposite X. In this position, the electro-motive force roduced across (I, c, by the small field F will cause the exciting current to flow from (Z, to c, and reach its maximum value at this instant and not being opposed b any other currents, this exciting current wi 1 produce the main alternating field flux represented by the heavy arrow F which will reach its maximum value at this instant. The rotation of the winding 8, through this field will produce an electro-motive force across the oints a, b, at right angles to the field, which will be counter to the applied electro-motive force at those points, and just enough less in value to permit the energy com )onent of current to flow to produce the small field F. Fig. 3, represents conditions corresponding 1 to an instant intermediate between those of y Figs. 2, and 4,-t. 6. one quarter ol a primary cycle later than the instant ol" Fig. 2. At this instant the clectro-motive force applied to the points (Z, c, is a maximum, producing, l by a small ilow of energy current the small l field F This by its rotation in the direction l of the dotted arrow produces a small electromotive force across (t, b, and-cause: a wattless magnetizing current scribed. One component of this current is neutralized by the flow of current in the points X and Z, while that component which is not thus neutralized produces the field F which is of smaller value than that in Fig. 4, being reduced by only a component of the magnetizing current instead ol' the whole. The value of F in Fig. 3, will in tact correspond to the 45 point in a sine curve whose maximum (Fig. 4) is at- 90 and the successive values of this field will winding 7 between the \follow the harmonic law. In Fig. 3, the

counter clcctro-inotive force between the has reached its maximum value and is produced partly by the rotation of the winding 8, through the field F and v i 2 partly by the rate ol increase of the held it The counter clcctro-motive lorce across a, 0,

points d and (a,

is zero, since the cll'cct ol' the rate of increase l ol" the hold F is neutralized by the rotation 1 ol' the winding 8. l Summarizing the above explanation it will 1 be seen that so long as the rotation ol' the I, rotor is maintained at hall synchronous i spend, thcrc'will be maintained an alternating licld across the points W, Y, which will develop in the windingH, clcctro-motivc forces counter lo the applied electronnotivo ll'orccs ol; the supply line, and an alternating to llow above dosashes electro-motive force 8,ac'ross the points W, Y, of half the priniary tirequency.

'der the conditions illustrated F ig'si 2 3,

and 4, a speed of rotation of the rotor equal to half thatiof synchronism will be autoinatically'maintained; During the halfprirnary *cyole ela'psing between'Figs. 2 and 4, the di count of the'reversalfof the field F (which rection of the resultant. wattless magnetizing current has shiftedf-ronimaximum flow into thc'windin 8,- at the point c, in Fig. 2, to maximum i'low into said winding at point (Z, in Fig. 4, and during this time there was always one component of thiscurrent at right angles to the principal alternating field F in the direction toproduee by its reaction on said field a torqueretarding the rotation.- During the. half cycle immediately preceding this, the action was exactly" reversed, on acwas'passing through its zero valuein Fig. 2),

" rightangles to the field F would reverse in direction just before the rotor reaches the position shown inFigfl 4. The duration oi" thcretarding torque would then he soihewhat less than a half cycle, and the duration oi the acceleratingtorque somewhat greater, producing a net torque tending to accelerate therotation,and bring the. rotor hack to its ndrmal' phase position. Similar-iv, ii the retort-should be slightly accelerated by any cause," and run a 'l similar to jthosd in' an ordinar ethflrefore be in air taiired f plies only, und e1;

developed asnet torque';tendingto r tard it.

The rotation at half. sfynichl onou's pr us fin'alys condijuor I rent is a to {tlpmin'th tween the points andjf lowed to flow hetweerith an outside circuit re-actions" owed , increase to appro gnnz t of hall'syncli.i:oni in U I in mind that the torque avaihihle for holding the rotor at half speed is limited to the reaction between the magnetizing current and the main field flux, so that it a i'oree in excess of this should be applied to the rotor it 5 would be thrown out 0 step. i nder the conditions ;illustrated in Fig. l, nmrr ar, with the winding 7 connected at the p' at;

W and iifimrallel with the aiteruatorii, re

The following analyv that tn rttl ahead. of"itsFnormal, phaseposltion, there wouldiiiirrwkliaiely he" f 1 the on tpu t from N I'Y isineutralized.

I- must also be home actions producing -1narke l.:stabi1ityare in- 'troduced; Uiider these conditions a slight retardation of the rotor Rand the'altcrnator fieldwill havethe'efi'ect of retardin the phaseof the eletro niotive force: Cleve oped in'fthe alternator,and at the same time advancing the phase ofthe electro motivefforce developed at the points W and Y. This latter result will'beproduced because of the "fact that the rotation of the magnetizing current in the winding 8, is opposite in direction to. the mechanical rotation. This change of phase relation between the two machines will have the well known result of causing a transter of current from the machine whose electro-n1otive force has been advanced into the niachine whose electro-motive force has been retarded, that is, in this case from the induction machine I into the alternator G. The result of this will he to produce a strong torque tending to accelerate the rotation of the alternator field, and also a torque tending to accelerate the rotor of the induction machine I, since output of the current from the machine at the points W and Y will produce the accelerating re-actions of the induction motor. It will be seen, therefore, that the torque developed in both machines incident to a retardation of the revolving members will tend to bring thorn back to normal phase position. Theoppositc efiect-Will of course he produced should slight acceleration occur.

It remains to show that the load of the translating devices L will be equally divided between the two machines and will roduce a balanced load on the two phases 0 the supply circuit 3, 4, ii. Assumefirst thata certain output of current is taken from the winding 7, at points W; Y", to supply a part of the load. on the consumption circuit 1, 2. The etl'eet of this output will he to cause an "equivalent injput to flow from .thehoonducto 4,- into the winding SQ -By referring to Fig; it-will he-scen .thatfthis're sult must T i take place for an ,out'put oi' ourrenti froin W,

Y," will tend to neutralize ,tl i e nagnetizing ndtheretore; alreary explained, reduce i th eorurter electrosnrotiveforoe atthe points (1, l) and thi's"reduction :will (151M391. ,tl flow into (1 b, from theasupplycircuit until At the h'istant represented bytFigt 2, efore, the entire energy output irinnrW, =1 will be supplied by an equiv'aIlei-it input from the supp y. circuit at the points (1., b. At the instant rep l resented by Fig 3, the output from W, 'Y, is

'reduced in the ratio o5" sine 45:1. The input at a, 7;, is now reduced to Zero, while the input at o, c, is atiits maximum, one conil ponent of 'vl hich halames the output from] "W, Y, wh the other is balanced by a how of current between the points Z, X, in the/short 13o as much energy will be connected synchronous circuit'connection. The latter, by its reaction on the main field flux F produces an accelerating torque. In order that the maximum instantaneous value of the input at d, c, in Fig. 3, shall have a component balancing the output from W, Y, at that instant, that maximum input value must be equal to the maximum value of the latter output. It will be seen therefore, output is taken from the points W, Y, twice delivered to the winding 8, from the supply circuit 3, 4, 5, 6, (equally divided between the two phases) one-half of which will be converted into mechanieal work. If the output of the alternator G, is equal to the output taken from W, Y equilibrium will result. If the output of G, is less, the revolving members of the twomachines will accelerate due to the surplus of mechanical energy developed in the rotor P, until the resulting change in phase position has e ualized the outputs from the two, when equi ibrium will be restored.

One of the advantages of the combination described above consists in the reduction in the capacity of machinery required to produce a given output. For example, 1 a standard motor generator set were utilized to deliver one thousand k. w. phase line, two machines each having a capacity of 1000 k. w. would be required. With the combination described herein each machine need have a capacity of only 500 k.

in order to deliver a total output of 1000 k. w. While it is true that the induction machine under these conditions would receive 1000 k. w of electrical energy irom the polyphase line, one-half of this energy is transformed inductively. If this'machine were designed to operate as a standard induction motor at the same speed, its capacity would be reduced to 500 k. w.

While the above description refers to the transfer of the electric energy from the poly-. phase circuit to the single phase circuit, it will be understood that the apparatus described may be used for the transfer oi en ergy in the opposite direction. The interand induction machines may also be used as a motor for developing mechanical energy. When the switch K, is in the position shown in Fig. 1, a speed corresponding to one-half the speed of syncln'onism with the polyphase circuit will be maintained. When the switch K, is thrown into contact with conductor l4, a speed of approximate synchronism with the polyphase circuit will be maintained, the machine 1, running as an ordinary induction motor. and the machine G being idle.

What i claim is:

l. In combination a pol 'phasc alternating current circuit, a single phase alternating current circuit, a synchronous dynamo-electric machineconnected to the single phase that when a certainto the single circuit, an induction machine provided with stator and rotor windings, whereof one is connected to the polyphase circuit, and the other is connected at appropriate points to the single phase circuit; means for short (is euiting the latter winding across other poin 1,- displaced trom the first mentioned points; and mechanical means for maintaining a fixed relation of rotation between the two machines. I r 2. In c61nbination a synchronous dynamo electric machine and mechanically Conner thereto an induction machine provided with rotor and stator windings, whereof on" is adapted for connection to a polyphase c cuit; means for connecting appropriate points of the other of said windings to the synchronous machine, and an independent circuit connecting other points in said winding.

3.- In combination a polyphase alternating current circuit, a single phase alte' current circuit, a synchronous dyiia tric machine connected to the single ph circuit, an induction machine provided stator and rotor windings, whereof connected to the polyphase circuit andthe other is connected at appropriate points to the single phase circuit; means for short circuiting the latter Winding across other points displaced from the first mentioned points; and means for maintaining a fixed relation of rotation between the two m achincs.

4. A polyphase alternating current circuit, a single phase alternating current ci cuit, an induction machine provid and rotor and their respectit nections from one of said windings polypliase circuit; means l'or coi propriate points in the other wirn in single phase circuit; a circuit of lo r:

connecting other points of: the tioned winding; and (lYllz'lllltt-(PlGCtih an ratus adapted to interclmn, blr' tran mechanical and elect s i l ratus connected ele v phase circuit and mecl 1. of said induction maclu 5. in combination a synchrono: 15; d3 12am electric machine, an induct machine provided with rotor and stator wn'idings, where of one is adapted for connection to a polyphase circuit; means for connecting appropriate points of the other of said windings to the synchronous machine; an independent circuit connecting other points in the last mentioned winding; and means for transferring between the two machines mechanical energy developed in either.

In testimony whereof l have hereunto signed my name.

JOSEPH liES'lllll l'l'GQDBlllilGE.

Witnesses: I

W. J. JACKSON, FRANK E. FRENCH.

Err 

